This invention relates to apparatuses for detecting the level of fuel oil in a tank of a vessel over a wide range of from the level of a sensing hole and a level sufficiently high above the sensing hole, and more particularly an apparatus in which a critical overflow level corresponding to the trim of a vessel can be readily, accurately and safely detected, whereby it is possible to fill the tank with fuel oil to a suitable quantity and to prevent the fuel oil from flowing over the tank.
Accidents concerning fuel oil overflow in vessels, in general, result in heavy losses. For instance, the overflow of fuel oil of one ton leads to the loss of one hundred million yen. Most of the causes of the accidents are mishandling of fuel oil during the fuel oil filling operation.
Accordingly, in order to prevent such an accident, it is absolutely necessary to accurately detect if the level of fuel oil reaches the critical overflow level. In the case where a vessel has a trim, the critical overflow level is varied in accordance with the trim, and therefore it is required to detect the critical overflow level corresponding to the trim.
There have been proposed a number of apparatus for detecting such a critical overflow level. For instance, a level gauge and a differential pressure signal generator are known in the art. However, these conventional apparatuses are disadvantageous in that they are too intricate in construction and accordingly too high in cost, and are rather difficult in handling and yet low in accuracy.
The application has proposed a critical overflow level detecting apparatus, as shown in FIG. 1, before. In this apparatus, a sensing pipe 1 having a sensing hole 2 at the lower portion is provided. The sensing pipe 1 is inserted into a fuel tank, and air is fed into the sensing pipe 1. The air is discharged out of the sensing hole 2. As the fuel oil level is raised, the sensing hole 2 is covered with the fuel oil, whereupon the pressure in the sensing pipe 1 is increased. In response to the pressure thus increased, an alarm is issued, thus detecting the critical overflow level. This apparatus is advantageous in that the operation is simple, and the critical overflow level can be detected positively and safely. (Japanese Utility Model Application No. 29250/1977).
However, the apparatus described above is still disadvantageous in the following points:
If, in the case where the position of the sensing hole 2 has been determined on the basis of the maximum trim of a vessel as shown in FIG. 2, a fuel oil filling operation is carried out with the vessel having no trim, then the alarm will be issued before the level of fuel oil reaches the critical overflow level DH, as a result of which it is impossible to sufficiently fill the tank with fuel oil. In contrast, if, in the case where the position of the sensing hole 2 has been determined to a position 2' with the vessel having no trim, the fuel oil filling operation is carried out with the vessel in the maximum trim, then the alarm will be issued after the level of fuel oil is excessively raised over the critical overflow level (DL). In this case, undoubtedly the fuel oil is caused to flow over the tank. This will become more significant in the case where as indicated by the phantom line in FIG. 2, the position of the sensing pipe 1 is closer to the side wall of the tank. Especially when the existing sounding pipe is employed as the sensing pipe 1; the above-described phenomenon takes place significantly, because the sounding pipe is, in general, provided along the side wall of the tank.